package network;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Created with IntelliJ IDEA.
 * Description: TCP回显服务器
 * 客户端发啥样的请求，服务器就返回啥样的响应
 * User: Li_yizYa
 * Date: 2025/5/21
 * Time: 20:19
 */
public class TcpEchoServer {
    private ServerSocket serverSocket = null;

    public TcpEchoServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }

    public void start() throws IOException {
        System.out.println("启动服务器");
        ExecutorService service = Executors.newCachedThreadPool();
        while (true) {
            Socket clientSocket = serverSocket.accept();
            // 创建线程，每个线程服务一个客户端
//            Thread t = new Thread(() -> {
//                try {
//                    processConnection(clientSocket);
//                } catch (IOException e) {
//                    throw new RuntimeException(e);
//                }
//            });
//            t.start();
            // 使用线程池
            service.submit(() -> {
                try {
                    processConnection(clientSocket);
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            });
        }
    }

    // 针对一个连接，提供处理逻辑
    private void processConnection(Socket clientSocket) throws IOException {
        // 先打印一下客户端信息
        System.out.printf("[%s:%d] 客户端上线!\n", clientSocket.getInetAddress(), clientSocket.getPort());
        // TCP 是全双工的通信，一个 socket 对象，既可以读，也可以写
        // 获取到 socket 中持有的流对象
        try (InputStream inputStream = clientSocket.getInputStream();
             OutputStream outputStream = clientSocket.getOutputStream()) {
            // 使用 Scanner 包装一下 inputStream，就可以更方便的读取这里的请求数据了
            while (true) {
                // 1. 读取请求并解析
                Scanner scanner = new Scanner(inputStream);
                PrintWriter printWriter = new PrintWriter(outputStream);
                if (!scanner.hasNext()) {
                    // 如果 scanner 无法读取出数据，说明客户端关闭了连接，导致服务器这边读取到 “末尾”
                    break;
                }
                String request = scanner.next();
                // 2. 根据请求计算响应
                String response = process(request);
                // 3. 把响应写回给客户端
                // 此处可以按照字节数组来写，也可以右另外一种写法
                // outputStream.write(response.getBytes());
                printWriter.println(response);
                printWriter.flush();

                // 打印日志
                System.out.printf("[%s:%d] req=%s; resp=%s\n", clientSocket.getInetAddress(),
                        clientSocket.getPort(), request, response);
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            System.out.printf("[%s:%d] 客户端下线!\n", clientSocket.getInetAddress(), clientSocket.getPort());
            clientSocket.close();
        }

    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer server = new TcpEchoServer(9090);
        server.start();
    }
}
